Patent No. DE 38 10 143 C1, discloses a coffee machine with a metering device. The metering device has an actuating element in the form of a screw conveyor that is positioned at the outlet of a container filled with dosing material. The revolutions of the screw conveyor determine whether more or less dosing material is discharged at a discharge port into a funnel situated under the discharge port. In this metering device, the funnel is located in direct contact with the brewing chamber. When the coffee machine is used several times in succession, hot steam originating from the brewing chamber can rise and moisten the discharge port of the metering device during the time period when the funnel is opened toward the brewing chamber to introduce the dosing material.
After a period of time, this process can lead to an accumulation of moisture on the discharge port. As a result, the dosing material being discharged adheres to this moisture on the discharge port. As the quantity of dosing material accumulating on discharge port increases over time, the discharge port becomes increasingly constricted. Ultimately, this can result in the discharge port becoming completely clogged, which results in the complete failure of the metering device.
Additionally, the dosing material adhering to the discharge port is constantly moistened by the rising steam. This can result in the dosing material caking and even turning moldy or growing harmful bacteria after extended use. This may lead to the metering device rendering the coffee inconsumable.